Spray nozzles with spiral flow fluid



Oct. 6, 1970 F. F. POLNAUER SPRAY NOZZLES WITH SPIRAL FLOW FLUID 4Sheets-Sheet 1 Fi led Feb. 23, 1967 FIG.

Oct. 6, 1970 F. F. POLNAUER SPRAY NOZZLES WITH SPIRAL FLOW FLUID 4Sheets-Sheet 2 Filed Feb. 25, 1967 R E U A N m 0 MP EF l NV FREDERICK ZATTORNEYS Oct. 6, 1970 F. F. POLNAUER 3,532,271

SPRAY NOZZLES WITH SPIRAL FLOW FLUID Filed Feb. 23, 1967 4 Sheets-Sheet5 INVENTOR FREDERICK F. POLNAUER BY M ATTORNEYS V SPRAY NOZZLES WITHSPIRAL FLOW FLUID Filed Feb. 23, 1967 4 Sheets-Sheet L I INIVEIQTOR 0FREDERICK s POLNAUER ///i 4/ BY ATTORNEYS 3,532,271 SPRAY NOZZLES WITHSPIRAL FLOW FLUID Frederick F. Polnauer, 250 Riverside Drive, New York,N.Y. 10025 Filed Feb. 23, 1967, Ser. No. 618,172 Int. Cl. A26c 1/06; B]:1/34 US. Cl. 239-1 19 Claims ABSTRACT OF THE DISCLOSURE This inventionrelates to spray nozzles and in particular to an improved nozzle for thedistribution of fluids, such as liquids, gases and other sprayablematerials, into a cone-shaped spray of very fine droplets that aredischarged in a uniform pattern and wherein the pressure head of thefluid to be sprayed is efficiently and effectively converted intokinetic energy of rotation in a circulation chamber.

BACKGROUND OF THE INVENTION Spray nozzles of the type using alogarithmic spiral flow for the fluid, are known in the art. In one suchnozzle, which is described in British Pat. No. 760,972, it is claimedthat optimal flow conditions caused by the formation of a logarithmicspiral flow, and thus maximum spray nozzle efficiency, can be obtainedby controlling (or is substantially dependent upon) only two majornozzle dimensions. These dimensions are the inlet width and largestradius of the swirl chamber, that is, the chamber in which thelogarithmic spiral fluid flow is obtained. The aforesaid British patentstates that a ratio of inlet width to largest radius not larger thanshould be maintained in the swirl chamber. However, 1 have found thatsuch a conclusion is not valid for most cases and instead, criticalratios among at least six parameters of the nozzle are of decisiveimportance in obtaining an effective nozzle. Further, I have found thatthe existing nozzles of this general type are lacking in many aspects ofproviding a good mechanical design wherein nozzle parameters may bereadily changed by replacing nozzle components and at the same timemaintaining certain predetermined relationships between the nozzlecomponents such as alignment of the outlet orifice with the axis of theswirl chamber.

SUMMARY OF THE INVENTION In accordance with my invention, an improvedspray nozzle of the logarithmic spiral flow type is provided in whichthe outlet orifice opening is concentrically aligned with the axis ofthe swirl chamber at all times. Further, in accordance with a preferredembodiment of my invention, a spray nozzle is provided which has areplaceable outlet orifice plate and a replaceable swirl chamber so thatthe total configuration of both the outlet orifice plate as well as theswirl chamber may be varied and combined according to certain conceptswhich are an important part of this invention to attain maximumperformance efficiency under a wide range of operational conditions.

United States Patent 0 3,532,271 Patented Oct. 6, 1970 In addition, inaccordance with the present invention, I have developed certain novelmethods and certain design criteria for determining the parameters oflogarithmic spiral flow spray nozzles which enable such nozzles to bedesigned with a considerable degree of predictability of sprayperformance, i.e., fluid flow rate and spray cone angle, rather than bythe usual cut-andtry methods. Further, I have also developed certainnovel methods and design criteria by maintaining ratios of nozzleparameters within predetermined ranges, which enable the patternationindex of a logarithmic spiral flow, spray type nozzle to be describedand predicted. A

It is therefore an object of this invention to provide a spray nozzlewherein the fluid flow characteristics approach the theoreticalflow-dynamics of a preferably logarithmic spiral resulting in anaxial-symmetric flow and a uniformly distributed atomized fluid forminga conical spray and wherein the energy losses through friction andparticle impact are minimized.

A further object is to provide a spray nozzle in which the outletorifice can be readily kept in alignment with the axis of the swirlchamber.

Still another object is to provide novel methods for mathematicallydetermining the parameters of logarithmic spiral flow type nozzles inorder to achieve certain operational characteristics.

An additional object is to provide novel methods and design criteria foruse in constructing logarithmic spiral flow type spray nozzles in whichthe patternation index can be maintained below a given value.

A further object is to provide novel methods and design criteria whichpermit the description and prediction of the patternation index of alogarithmic spiral flow spray type nozzle.

Another object is to provide novel methods and design criteria used inthe construction of logarithmic spiral fiow type nozzles in which thespray performance can be predicted.

Other objects and advantages of the present invention will become moreapparent upon reference to the following specification and annexeddrawings, in which:

FIG. 1 is a longitudinal cross-sectional view through the center of oneembodiment of the spray nozzle constructed according to the principlesof the invention;

FIG. 2 is a top plan view of the swirl chamber body shown in FIG. 1,with a swirl chamber whose wall is shaped according to a logarithmicspiral;

FIG. 3 is a longitudinal cross-sectional view taken along line 3--3 ofFIG. 2;

FIG. 4 is a cross-sectional view taken along line 44 of FIG. 2;

FIG. 5 is a top plan view of the orifice plate;

FIG. 6 is a cross-sectional view of the orifice plate taken through line66 of FIG. 5';

FIG. 7 is a longtiudinal cross-sectional view through the center of afuel injection spray nozzle made in accordance with the principles ofthe present invention;

FIG. 8 is a cross-sectional view taken along line 88 of FIG. 7;

FIG. 9 is a cross-sectional view taken along line 9-9 of FIG. 7;

FIG. 10 is a top plan of the nozzle of FIG. 7;

FIG. 11 is a bottom plan view of the nozzle of FIG. 7;

FIG. 12 is a longtiudinal cross-sectional view through the center of afuel injection nozzle for gas turbines made in accordance with theprinciples of this invention;

FIG. 13 is a top plan view of the nozzle of FIG. 12;

FIG. 14 is a longitudinal plan view of the nozzle of FIG. 12;

FIG. 15 is a longitudinal sectional view through the center of anotherembodiment of the fuel injection nozzle 3 for gas turbines according tothe principles of this invention;

FIG. 16 is a longitudinal sectional view through the center of a furtherembodiment of a fuel injection nozzle for gas turbines, according to theprinciples of this invention;

FIG. 17 is a sectional view of an improved embodiment of the orificeplate; and

'FIG. 18 is a sectional view of an improved embodiment of the swirlchamber.

Referring to FIG. 1, a preferred embodiment of a spray nozzleconstructed according to my invention comprises a housing 1 of steppedcylindrical shape with a male thread 5 formed along a portion of itslargest outer diameter. The one open end at the top of the housing 1 hasa bore 6 in which a swirl chamber body 2, having a bottom wall 12 and achamber 9, and an orifice plate 3 are located. The lower end of housing1 contains longitudinal inlet bore 7 concentric with the longitudinalaxis AA of the body provided with a female thread 8 into which theliquid to be sprayed is admitted.

The swirl chamber body 2 and orifice plate 3 are tightly fitted into thebore 6 to prevent leakage from the bore 6 of housing 1. As seen, bothparts 2 and 3 are readily removed from the bore 6 for the purpose ofreplacing them. The orifice plate 3 has an orifice and the body 2 has achamber 9 both of which are concentric with the longitudinal axis AA ofthe body. This concentric arrangement of orifice plate 3 and swirlchamber body 2 within the bore 6 of housing 1 is of great importanceregarding the capability of mass-producing this type of nozzle with ahigh degree of precision and maintaining very small dimensionaltolerances. Since the bore 6 serves as a gage, or master, for theperipheral diamenters of swirl chamber body 2 and orifice plate 3, thisarrangement is important for making it possible that differentreplacement parts of 2 and 3 will always fit into the housing. Suchreplacements will be required whenever these parts have been worn off ordamaged by usage or must be replaced to accommodate varying operationalconditions.

Swirl chamber body 2 and orifice plate 3 are firmly held in place withinthe housing bore 6 by a threaded cap 4 which presses down upon the uppersurface of the orifice plate 3, and thereby also prevents leakage of thefluid from the body. A seal 11 may also be used between the body upperwall and the cap to prevent leakage. The inner wall of the cap 4 carriesa female thread 5a to engage the male thread 5 of housing 1.

After passing from a fluid supply conduit (not shown) through the inletbore 7, the liquid flow enters an inlet 13 (see FIG. 2) which istangential to the inner wall 14 of the swirl chamber 9. The fluid iscirculated in chamber 9 along a generalized logarithmic spiral and isdischarged through the outlet orifice 10 in the shape of a hollow cone11 (FIG. 1). The axially symmetric thinwalled conical shell ofdischarged fluid at the outer edge of the outlet orifice 10 is tornapart into very fine droplets due to the effect of the centrifugal forceof the circulating fluid.

In FIG. 2, the swirl chamber body 2 is shown in a top plan view and theflow path of the fluid entering the tangetial inlet 13 is indicated bythe arrow. According to FIG. 4, which represents a sectional view alongline 4-4 of FIG. 2, the liquid passes upwardly through a cutout 12a inthe bottom section 12 through inlet passage 13 and thereafter thinninginwardly above the bottom wall 12 of the swirl chamber into a horizontalposition. FIG. 3 is a longitudinal sectional view along line 3-3 of FIG.2.

From FIGS. 2 and 3 may be seen four major dimensional parameters of thisspray nozzle considered as important, according to my invention, whichaffect the etliciency and effectiveness of the performance of the spraynozzle. They are the height of the Swirl chamber H; largest radius ofthe swirl chamber R; width of the tangential inlet B close to the inletopening into the swirl chamber; and the thickness of the rib S formed bythe inner wall of the swirl chamber at the inlet. The inlet side wall 14of the swirl chamber 9 is preferably shaped according to an outer turnof a true logarithmic spiral.

It has been found, in general, that a logarithmic-spirally shaped swirlchamber is preferable in efiiciency to a circularly shaped chamber.However, there may be varying conditions under which it would sufiice touse variations to the logarithmic spiral, e.g. circular chambers. Withregard to the number of inlets into the swirl chamber, it can be statedthat one inlet is generally most preferable since it causes a minimum ofclogging and inner fluid friction.

FIG. 5 shows the orifice plate 3 in a top plan view and FIG. 6 shows asectional view of FIG. 5. From FIG. 6 may be seen the two other majordimensional parameters, the diameter D of the outlet orifice 10 and theaxial thickness L of the orifice plate near the outlet orifice. The coneangle 2 b of the hollow spray cone formed by the fine droplets is shownin FIG. 6.

FIGS. 7-11 show another embodiment of my invention which is useful inapplications such as fuel injection in oil burners or in any type ofcombustion chamber. The same reference numerals are used for similarparts, where applicable. This embodiment comprises a housing or nozzlebody 16 of generally cylindrical shape with two sets of male threads 17and 18 formed on two different portions of its outer diameter. One openend of body 16 has a concentric longitudinal bore 19 in which the swirlchamber body 2 and orifice plate 3 are located, as in FIG. 1. The lowerend of housing 16 has a concentric longitudinal bore 20, of smallerdiameter than bore 19, into which the fluid to be sprayed is admitted.

The swirl chamber body 2 and orifice plate 3 are closely fitted into thebore 19 to prevent leakage from the bore 19 and the nozle body 16. Bothparts 2 and 3 are easily removed from the bore 19 for replacementpurpose. Swirl chamber body 2 and orifice plate 3 are firmly held inplace within the bore 19 of the housing 16 by a threaded cap 21 whichbears down under pressure upon the upper surface of orifice plate 3, andthereby also prevents leakage of the fluid. The inner wall of cap 21 hasa female thread 17a engaging into the male thread 17 of nozzle body 16.As in FIG. 1, the swirl chamber and the outlet orifice are heldconcentric with the longitudinal axis of the nozzle by the inner wall ofbody 16 surrounding bore 19 which extends above the swirl chamber bodyand engages a portion of the orifice plate.

The threads 18 are provided to engage corresponding threads of thecombustion chamber, or any fitting to hold the nozzle body 16. Thefitting or chamber reaches a stop against a shoulder 16a.

FIGS. 12-14 show a further embodiment of my invention which hasparticular utility for fuel injection in combustion chambers of gasturbines. As seen best in FIG. 12, the spray nozzle of this embodimentincludes a housing or nozzle body 22 of cylindrical shape with two setsof threads 23 and 24 formed on two difffierent portions of its outerdiameter. One open end of nozzle body 22 has a longitudinal bore 25 intowhich the swirl chamber body 2 and orifice plate 3 are closely fitted.Again, the outlet orifice 10 and swirl chamber 9 are concentric with thelongitudinal axis of the body and the bore. The opposite end of housing2 contains a concentric longitudinal bore 26 of reduced diameter throughwhich the fluid to be sprayed is admitted.

Swirl chamber body 2 and orifice plate 3 are closely fitted into bore 25to prevent leakage within bore 25 and nozzle body 22. Parts 2 and 3 caneasily be removed from bore 25 if so required. Both parts 2 and 3 arefirmly held in place within bore 25 by a threaded cap 27 which pressesdown on the upper surface of orifice plate 3 and thus also preventsleakage of the fluid. The inner wall of cap 27 carries a female thread23a which engages the 1 corresponding male thread 23 of housing 22.

The peripheral portion 28 of cap 27 is of circular configuration and itsdiameter can accommodate the inside diameter 29 of an air shroud member30. The purpose of air shroud 30 is to coll the surface of the nozzleand to keep it free of harmful deposits. This is accomplished byintroducing an air stream through several longitudinal channels 31provided in the cylindrical outside portion of cap 27. The air flows upto the inner wall 33 of the top portion of the shroud and is thereproperly distributed over the face of the nozzle. The inside diameter 29of shroud 30 fits tightly on the peripheral portion 28 of cap 27, and isthus firmly held in place. Several longitudinal cutouts 32 in the shroudequal in number and matching with the longitudinal channels 31 of cap 27enable the air to enter the shroud.

A lock ring 39a locks cap 27 and body 22 firmly together and thusprevents loosening of the connection provided by the threaded portion 23of nozzle body 22. The male threaded portion 24 serves to fit the nozzlebody 22 into a female threaded fitting contained in the combustor wall,or in a main manifold distributor if the combustion chamber has morethan one nozzle.

A cylindrical filter 34 of the cartridge type is placed within the bore26 at the lower end of housing 22 to filter the fuel. The filter screen34 is brazed to a collar 35 whose peripheral circular diameter 36 can beaccommodated within the inside diameter 37 of the cylindrical bore 38formed at the fuel inlet portion of the nozzle. A retaining snap ring 39holds collar 35 of filter 34 firmly in place.

FIG. 15 shows another embodmient of my invention which may also be usedfor fuel injection in the combustion chambers of gas turbines. In FIG.15 a swirl chamber body 40 of cylindrical shape is shown with two setsof male threads 41 and 42 formed on two different portions of its outerdiameter. The closed end of body 40 is integrally formed with the spiralswirl chamber 43. The outside diameter 44 of swirl chamber body 40 isclosely fitted into a matching inner bore of a cap 45, which is theorifice body 45 and which has formed at one end thereof the outletorifice 10. The inner wall of cap 45 carries a female thread 41a formating with the male thread 41 of housing 40. These threads 41 and 41amate on the body below the swirl chamber to preserve the axialalignment. The threaded cap 45 bears down on the upper surface ofhousing 40 and thus prevents leakage of the fluid. Again, the axis ofthe swirl chamber and of the outlet orifice are held in line with thelongitudinal axis of the body. However, the gage action accomplished bythe wall 6 of the main body bore in FIG. 1, is lost.

The peripheral portion 46 of cap 45 is of circular condiameter 47 of anair shroud 48. Several longitudinal cutouts 48:: are provided on theshroud 48 and matching longitudinal channels 49 in the cap 45, so thatthe air can flow to the inner wall 50 of shroud 48 and is there properlydistributed over the face of the nozzle. The inside diameter 47 ofshroud 48 fits tightly on the peripheral portion 46 of cap 45. Toprevent loosening of the nozzle assembly during operation, a fixed joint51 is provided to secure the assembly firmly.

The male threaded portion 42 serves to fit swirl chamber body 40 into afemale threaded fitting of the combustor wall or of a manifold fueldistributor. The strainer assembly 52 is similar to the one shown inFIG. 12.

FIG. 16 shows a further embodiment of my invention to be preferably usedfor fuel injection in gas turbines. This embodiment differs from theembodiment shown in FIGS. 14 and 15 in several respects. In FIG. 16 thenozzle body 53 is of cylindrical shape with two male threaded portions54 and 55 along two different portions of its outer diameter. Adjacentthe left open end of body 53 (as shown in the drawing) are located theswirl chamber body 2 and orifice plate 3. Body 2 and orifice plate 3 areclosely fitted into a bore 56 of a threaded cap 57 which holds parts 2and 3 firmly in place within bore 56 and aligned with the bore axis bypressing down on the upper surface of orifice plate 3, thus preventingleakage of the fluid.

The inner wall of cap 57 carries a female thread 54a to engage thecorresponding male thread 54 on body 53. Parts 2 and 3 can easily beremoved from bore 56 if so required. Similar to the nozzle shown in FIG.12, the embodiment of FIG. 16 also contains an air shroud 30, a lockring 39a and a strainer assembly 52.

FIG. 17 shows a sectional view of an improved embodiment of the orificeplate 3. Here, improved orifice plate 58 has an upwardly slightlyslanting inner wall 59 as shown in the drawing. This has been foundadvantageous in smoothly guiding the horizontal streamlines into avertical direction at the outlet orifice and thus minimizing fluidfriction.

FIG. 18 shows a sectional view of an improved swirl chamber useful withthe nozzles of the present invention. Here, the swirl chamber body 60contains a swirl chamber 61 with its bottom wall carrying a concentricconical ridge 62. This ridge has been found useful in smoothly guidingthe streamlines upward toward the orifice hole and thus minimizing innerfluid friction.

In all of the foregoing nozzle designs, it should be noted that theconcentricity of the orifice or orifice cover plate is independent fromthe concentricity (or lack of it) of the threaded portion of the capwhich holds the orifice cover plate down or which forms the orifice.This is highly advantageous. Further, in those embodiments where a capis used to hold the cover plate down, in assembling the nozzle andthreading the cap on the housing, no twisting or tilting stress isexerted on either the cover plate and/or the swirl chamber body whichcould otherwise lead to a distortion of both and causes eccentricity ofthe axis or deflection of it.

From the viewpoint of thermal stresses the nozzle design of my inventionis also advantageous for several reasons. For example, in a typicalapplication the temperature of the oil in a swirl chamber is F, whileoutside the nozzle in the combustion chamber it may be 1000 F. and atthe area of circulating air on the outer periphery of the nozzle about700 F. Therefore, temperature gradients are set up which may lead tobuckling or warping of the spiral swirl chamber body insert, andparticularly the cover plate. By letting the cover plate protrude abovethe upper rim of the housing body, the orifice cover plate obtains morestrength and resistance against buckling.

Heretofore, the theoretical advantages which should be possible in spraynozzles using a circulation chamber wherein a fluid film is torn apartby centrifugal force at the outlet orifice of the circulation chamber,have not been achieved. From investigations in this area I have foundthat the failure to achieve optimal results with this type of spraynozzle has mainly been due to large frictional losses, lack of anaxially-symmetrical flow and impact of the fluid particles within theswirl chamber and at its inlet and outlet passgaes. I have also foundthat these failures have been caused by a basic lack of understanding ofthe effect of the total nozzle geometry as represented by the siximportant geometric parameters, B, D, H, L, R and S, referred to above.

Heretofore, nozzles of the swirl chamber type have been designedprimarily by an empirical, or cut-and-try method with little regard tothe inter-relationship of the aforementioned six geometric variables.Further, the prior art design methods did not permit any advanceprediction as to efiicacy of the nozzle and its spray, for example, interms of the cone angle and weight flow rate of the fluid. Further, theprior art nozzles are not able to establish certain nozzle designcriteria by which a patternation 7 index of below a certain value can beachieved, or to predict the patternation index in general. The effectand use of the patternation index is described below.

When designing nozzles of the spiral swirl chamber type, two criteriaare usually specified by the purchaser for whom the design is beingmade. These are the cone angle (2 b) and the actual weight flow rate (Wof the fluid. Starting with these two criteria, the following is amethod that I have evolved which can be used for determining certain ofthe nozzles geometric parameters.

As is known, the discharge coefiicient (K) and spray cone angle (Zr/1)of a nozzle are functions of the geometric parameters of the nozzle andthe nozzle pressure drop. For a given nozzle having the followingproperties:

the weight flow rate for an ideal fluid (W is given by:

idea1 out V 'Y If we know the cofiicient of discharge (K) for aparticular nozzle pressure drop (AP), we can write the actual weightflow rate (W as:

act ideal It was found that the coefiicient of discharge at a givenreference pressure drop (K is an empirically derived function (f of thenozzle area ratio A /A By defining the area ratio as ir. or

then

( rer=f1( Further, it was found that the discharge coefficient K for anyAP can be related to the discharge coefiicient at the reference pressuredrop by a correction factor (C as follows:

K p ref The correction factor C is a function (f of the actual nozzlepressure drop, p=fz( In a similar manner, a set of empirically derivedfunctions relate the spray cone angle (Zip) for a particular actualpressure drop to the area ratio out Thus, the spray cone angle for thegiven reference pressure drop (2p is a function (f of the area ratio, asfollows:

To relate the spray cone angle 2x11 for any given pressure drop to thespray cone angle at the reference pressure drop (2% a correction factorf ref (degrees) f3 is used as follows:

2w mr The correction factor Cw is a function (f4) of the actual nozzlepressure drop, and is given by: 2=f4( To summarize, there are four basicempirically derived relationships to consider in defining the nozzle:

( ref f1( which states that the coefficient of discharge at a referencenozzle pressure drop of AP is a function (f of the area ratio.

( p=f2( which states that the correction factor used to adjust thedischarge coefiicient K for pressure drops other than the referencepressure drop is a function (f2) Of the actual nozzle pressure drop.

which states that the spray cone angle at a reference nozzle pressuredrop is a function (f of the area ratio. (4) C2=f4( which states thatthe correction factor used to adjust the spray cone angle to pressuredrops other than the reference pressure drop is a function (f of theactual nozzle pressure drop.

A nozzle can readily be designed in accordance with Equations 14, oncethe various functions f through f are determined. For example, considerthat a nozzle must be constructed that will give a given weight flowrate W and spray cone angle 231 at a given nozzle pressure drop AP.

First step Using Equation 4, calculate 02 for the given nozzle pressuredrop AP.

Second step We know that 1 2 re =4 l r Cw from the definition of Sincewe have from the First Step and 2 1/ is given, We can solve Equation 3for the area ratio out i.e., m 1 3 f out 02% Third step Using Equation2, calculate C for the given nozzle pressure drop AP.

Fourth step 9 We know from before that:

aet= ideal and 1dea1= out V 'l it follows that:

[Gm/ZyyAP where D is in ft., W in lbs./sec., 'y in lbs./ft. and AP inlbs./ft.

Sixth step 'By using the ratios of the other nozzle dimensions, asdefined by the requirements for good patternation which are discussed indetail below, we are able to determine the important nozzle dimensionsother than D. In this procedure one must bear in mind that nozzle inletarea A as defined by B H must be kept at such a level so that the ratioA /A remains at a value which is predetermined by the Second step.

It should be understood that by using the method described above, thatempirical relationships of the nozzle passages (parameters B, D and H)are established for a given flow rate and cone angle.

A typical procedure will now be described for deriving f f f and 1,which are used in Equations 1, 2, 3, and 4 above. Of course, any othersuitable procedure may be used in accordance with conventionallyaccepted techniques. In this procedure a family of logarithmic spraytype nozzles of similar design, but with different A (inlet area) and A(outlet areas), are operated over a wide range of nozzle pressure drops,for example from to 700 p.s.i. The spray cone angle (230) and the actualnozzle fiow rate (W are measured at specific values of pressure drops.From each of these measurements the value of the coeflicient ofdischarge for a given pressure drop can be computed as:

measured flow rate W 'y=fuel weight density A =nozzle outlet orificearea=1rD /4 and g gravitational constant.

In one specific run of the typical procedure being described,twenty-seven different nozzle combinations were used in determining Kand 2 1/ at various AP points, with three different D, H and Lparameters, while B, S and R were held constant. From the total oftwenty-seven, nine nozzle combinations were used to determine K and 21/1with D and H varying and the parameters L, B, S, and R being heldconstant. The twenty-seven nozzle combinations used were believed to besuflicient to provide the necessary data within the ordinarily acceptedlimits of experimental and design error. Of course, fewer or morecombinations can be used as the accuracy requirement dictates.

The data obtained in the run with the various nozzle combinations isplotted to give two families of curves. The first family represents K(ordinate) vs. A /A (abscissa) for the various nozzle combinations atgiven values of AP, each curve of the family being at one value of APfor nozzles of the number of available combinations. The second familyrepresents the measured 2\// (ordinate) vs. A /A for the various nozzlecombinations at given values of AP, each curve of the family being atone value of AP for the nozzles of the number of available combinations.

To make the data of the curves more easily usable for general analyticaldesign of the nozzles, the curves were translated into numericalequations to obtain 11, f f and L in the following manner:

Step 1.The discharge coefficient K is obtained from the first family ofcurves as a function of the A /A ratio.

(a) Since the discharge coeflicient K varies with nozzle pressure dropAP at a constant A /A value, a reference pressure drop is selected atwhich the K vs. A /A relationship is to be found. This gives K ofEquation 1. In the experimental run being described, a 300 p.s.i.pressure drop was selected as K to obtain f since this value is aboutthe center of the range of pressure drops tested. Of course, any othersuitable constant pressure drop line can be selected.

(b) The experimental data of K vs. A /A plotted at the 300 p.s.i.pressure drop is then curve fitted by any suitable manual or automaticcomputational method, for example the least square method. The lattercomprises applying the method of least squares to fit polynominals ofdegrees 1, 2, 3 and 4, of the form ref=f1( in out) through the data setsof pairs of values. This resulted in K at p.s.i., Or K300.

Step 2.To derive the correction factor C as a function 1 of the actualnozzle pressure drop AP in Equation 2, families of curves K vs. A /Awith pressure drops varying from 15 to 700 p.s.i. are again plotted. Thevalues of A /A ratios are from the same nozzle combinations used in Step1 and are identical with the respective values of A /A used in Step 1.The data for each nozzle pressure drop AP is taken from the experimentswith the various nozzle combinations.

If K is the actual discharge coefficient for any AP, the correctionfactor is As explained above, both K and K are derived from theexperimental data. As a second part of Step 2, all C values arecalculated for each given value Ai /A corresponding to the respective A/A values of the curve K, =f(x). It was found that in the nozles of thepresent invention, the C values at any specific pressure drop do notvary significantly for different area ratios. Therefore, the average Cdata can be plotted against varying AP and a fitted curve produced bythe least square method as used in Step 1. The fitted curve equationgives C =f (AP) Step 3.--To obtain the cone angle 2,0 as a function 73of the A /A ratio in Equation 3, a reference pressure drop is selectedsince the cone angle varies with nozzle pressure drop AP at a constant A/A value. In the experimental run being described, the 300 p.s.i.reference pressure drop was again used. The experimentally ob taineddata 2 0 vs. A /A plotted in the second family of curves is extractedfor the selected reference pressure drop and a curve plotted. This curveis then curve fitted 'by the least square method to give 2 l/ =f (x)Step 4.To obtain the correction factor as a function 2, of the actualnozzle pressure drop in Equation 4, so as to be able to adjust the spraycone angle 25b to pressure drops other than the reference pressure drop,the following is done:

(a) Families of curves 2\// vs. A /A are plotted with pressure dropsvarying from 15 to 700 p.s.i. The values of A /A are from the samenozzle combinations as used in Step 1 and identical with the respectivevalues of A /A of Step 1. The data for each cone angle is experimentallymeasured. If 2 1/ is the actual cone angle for any AP, the correctionfactor is 2 Wit.

1 l (b) Next, all

values are calculated for each given values A /A corresponding to therespective A /A values of the curve 2,.,,=f (x). It was found that theC211 values for the nozzles of the present invention at any specificpressure, do not vary significantly for different area ratios.Therefore, the averages data can be plotted against varying AP and afitted curve developed by the least square method as used in Step 1. Thefitted curve results in the equation As should be apparent, a completemethod has been described for either obtaining several of the nozzleparameters, if 2 h and W are given, or for predicting 2 h and W when theA /A ratio and pressure drop as known.

One of the most difficult requirements to be attained in swirl chamberspray nozzles using a circulation chamber is the atomization of a fluidinto fine droplets and discharging the atomized fluid into a uniformlydistributed conical spray. The latter property of the spray is of basicimportance in many applications of spray nozzles, and particularly forfuel injection in combustors of oil burners, gas turbines, and otherinternal combustion engines.

The degree of uniform weight distribution of the spray achieved by aspray nozzle can be measured by the socalled patternation index (delta)which represents a quantitative measure for the level of distribution.

For a better understanding of the patternation index concept which isinvolved in my invention, it is useful to present a short definition ofone of several ways by which a patternation index may be obtainedexperimentally. In one method of obtaining the patternation index, atotal number of X observations are taken on the percentage of fluidsprayed into, for example, six equal 60 sectors arranged in a circularor hexagonal catch basin. The sum of the absolute values of thedifferences between 16 /3% and the percentage falling into each of thesix sectors of the catch basin during each of the X test runs is used asthe patternation index.

In general, the lower the patternation index, the better thedistribution of fluid by the nozzle in the conical pattern. In manycritical applications, for example, a spray nozzle used for fuelinjection in the combustion chamber, a nozzle having a largepatternation index would cause uneven, damaging fuel concentrationsresulting in hot spots on the combustion wall or adjacent components,e.g., turbine blading.

In the calculation of the parameters of swirl chamber nozzles it is veryimportant to the designer to quantitatively evaluate as part of hisdesign procedure the effect of the various geometric parameters which hemust select in part arbitrarily. In accordance with this invention thepatternation index is used as an important and basic criterion for theevaluation of the design as related to the total nozzle geometry andalso to the quality of the manufacturing technique used to produce thistype of swirl chamber spray nozzle. The use of the patternation indexserves for optimization of the design and for manufacture evaluation.

The prior art of designing swirl chamber nozzles with a circulationchamber fails to obtain such aforementioned design criteria, andparticularly one containing the patternation index. It is an importantpart of my invention to use the patternation index as well as ranges ofratios of the six major nozzle dimensions as aforementioned, in a uniqueand novel way in describing and predicting the efficiency of nozzledesign in terms of performance in patternation.

It has been found that the optimal performance of a swirl chamber typewith one inlet and spray nozzle is significantly affected by the sixgeometric parameters or dimensions, namely, the orifice diameter D;axial thickness of the orifice plate L at the outlet orifice; width ofthe tangential inlet B close to the inlet opening into the swirlchamber; height H and largest radius R of the swirl chamber; and thethickness S of the rib formed by the inner wall of the swirl chamber atthe inlet. Each of these six geometric parameters are important foraccomplishing two novel and major features of this invention, namely thedescription and prediction of nozzle performance in terms of thepatternation index delta for a given set of these six geometricparameters.

It has been discovered that there is no single parameter whose value iscritical in itself. Instead, for any given value of a single parameterwithin a given range of geometric variables, stated subsequently, we canobtain optimal nozzle performance in terms of good patternation byvarying the other parameters within their stated ranges of limits.

It was found that each of the following ten geometric ratios:

constituting the geometric independent variables are the more importantones in determining the patternation index, but the value of any one ofthese does not fix the patternation performance.

It also was found that nozzles having a patternation index delta lessthan 30, are generally acceptable for many spraying purposes. However,in applications as critical as fuel injection in combustors of gasturbines, the patternation index should be much less than 30. Ingeneral, it was found that the reliability or consistency of thepaternation performance is very high for nozzles having a lowpatternation index.

Since all the six independent variables or geometric parameters D, L, B,R, H, and S contained in the above stated ten ratios are important andsince there is much interaction occurring among them, we cannot describegood nozzles by giving ranges on each variable separately. We canhowever, by defining regions for the above cited ten geometric ratiosachieve two major features of this nozzle, the description andprediction of nozzle performance in terms of the patternation indexdelta. It should be noted that description and prediction of theperformance in terms of the index delta are two separate features ofthis invention-and the conditions for each will be separately described.

The ranges of the ten ratios specified in Groups I and II above areobtained in the manner hereafter described, or in any other suitableexperimental and/or mathematical manner. The method to be described,however, has been found to be accurate to a relatively high degreewithin normally accepted limits of experimental error. As the firststep, a number of experiments involving different nozzle combinationswith varying combinations of parameters D, L, R, H, B and S are run andthe patternation index delta is measured for each experiment, The deltameasurement is carried out in any suitable way, for example, asdescribed above. The data from each experiment is used for latercomputational purposes and it is conveniently utilized on an electroniccomputer, so it is, for example, placed on punched cards or tape.

The second step is to find which of the six nozzle parameters are thevariables affecting patternation and which combinations (thereof) (suchas linear ratios, e.g., D/R; squares, exponential powers, etc.) must beinvestigated to determine their effect on the patternation behavior ofthe nozzle. As the first part of this step, the linear relationships ofall of the combinations of six variables are investigated, for exampleby using a stepwise multiple regression program in a computer, toeliminate all insignificant variables. After the insignificant variablesare eliminated a computer run is made to determines the most significantcombinations (linear ratios, etc.) of parameters. Further regressionanalyses are then made to further eliminate non-essential combinationsof parameters from this run. After all non-significant combinations ofparameters are eliminated an equation is derived which is the basicpatternation index delta equation. In the sample process beingdescribed, seven regression runs were made and the delta equation turnedout to be:

() (5) (PATTERNATION INDEX delta) L B S L B R -{Jr 5*!12 -+ga 54-94 54-95 m bidwhere g to g are factors representing influence coefficientsand K is a constant.

As the third step, the values of the most significant linear and squarecombinations of parameters are investigated. In the sample process beingdescribed, the following fourteen combinations of variables weretabulated for the various combinations of nozzles investigated. In thesample 243 nozzle combinations were used and 465 delta measurements weremade with them. The data from the tabulation of each of the furtherinvestigated combinations of (fourteen) variables is then plotted forvarious given ranges of delta, e.g. delta=2025, 25-30, 35-40. To stateit another way, a curve is made for delta (ordinate) vs. each one of thefourteen variables within a given range of delta. Each of the curves isevaluated to determine which of the variables influenced thepatternation index delta more significantly. This is done byestablishing a trend line and discarding those variables which indicatea small eifect on delta. To state it another way, those of the fourteenvariables indicating an undefinable effect on delta were discarded,i.e., a screening process is used. Those variables (of the fourteen)which indicated a more significant effect, are maintained.

As the fourth step, all of the computer regression analysis runs arescreened for the data points which do not fit Equation 5. Thisidentified those points where the regression analysis cannot predictpatternation. These points lying outside the predictable range ofEquation 5 established the critical ratios of Groups I and II.

The experimental data for the sample run described above on the variousnozzle combinations was made with water as the fluid at a gage pressureof 100 p.s.i. For fluids other than water, and pressures different than100 p.s.i., suitable correction factors for density, viscosity and fluidpressure must be applied. However, the general technique described fordetermining the ranges of the ten ratios of Groups I and II can be usedwith any fluid at any pressure.

For water, at 100 p.s.i., the following limits of the ten ratios have tobe observed for the following objectives:

(1) Description of performance.To describe the performance of allnozzles with a patternation index delta of less than, the ratios ofGroup I have to stay within the following limits:

These four ratios as defined by the stated limits are of primaryimportance and determine all five nozzle dimensions with the exceptionof S. The ratios of Group II offer refinements in the definition of thefour above ratio parameters. Group II comprises the ranges:

The ratios of Group II are criteria for confirming or rejecting theratios of Group I with regard to their suitability for describing nozzleperformance. The ratios of of Group II are capable of screening possibleselections of dimensions which are not compatible within themselves.

(2) Prediction of perf0rmance.In order to be able to predictperformance, this capability is determined by the ranges of threeratios:

If we stay within the limits of these three ratio parameters, We canpredict the performance of a nozzle in terms of the patternation index.It must be noted that nozzles designed within the limit of R/ D, L/ Dand S/D will have a predictable performance, but not necessarily a goodperformance.

In summary, the use of the ten ratios discussed above enable a nozzledesigner toobtain a nozzle with a patternation index below a certainvalue, thirty in the example described with the ranges stated. The useof the three ratios R/D, L/D and S/D also permit the prediction ofnozzle performance in terms of the patternation index delta.

Further, Equation 5 enables a nozzle designer to ob tain by mathematicalanalysis the patternation index delta for my nozzle. This is extremelyuseful since it tells the designer whether or not the nozzle he designshas the required patternation index.

Nozzles constructed in accordance with my invention have manysignificant advantages. Some of these are:

1) The ability to maintain a substantially constant angle of spraythroughout a wide range of volume output under varying pressure heads ofthe fluid.

(2) The ability to maintain a fairly constant coefllcient of dischargeover a wide range of pressure heads and a wide range of volume output.

(3) Very fine droplets at relatively low fluid pressure.

(4) A minimum of pressure variation between the largest and smallestvolume output, or flow rate, in order to keep the maximum pressure low.

(5) Ability to have relatively large cross sections for passage of thefluid to minimize the change of clogging.

(6) Uniform weight distribution of the droplets in the conical spray,i.e., good patternation over a wide range of volume output.

(7) Production of fine droplets maintained over a Wide flow range.

(8) High quality of atomization and high level of patternation aremaintained over a relatively long life span of the nozzle.

(9) When used for fuel injection into combustion chambers, stablecombustion, high combustion efiiciency and faultless ignition under mostunfavorable conditions over a long life span of the nozzle.

(10) Etficient and effective operation when atomizing highly viscousfluids or fuels.

(11) Long life span of the nozzle.

(12) Effective and efficient operation of designs for smallest andlargest volume output.

(13) Maximally attainable ranges in flow rate.

(14) Simple designs which are rugged in construction, can well resistoperational stresses, e.g. due to thermal stresses.

(15) Simple designs with very few component parts Which are suited forhigh-precision production, highest surface quality, best assemblingmethod and easy maintenance and replacement of the components.

(16) Simple designs which allow mathematical prediction of mainperformance parameters such as patternation, coefficient of dischargeand spray cone angle. This avoids design and construction by costly andtimewasting cut and try methods.

(17) High combustion efficiency over a wide range of fuel/ air ratios.

While preferred embodiments of the invention have been described above,it will be understood that these are illustrative only, and theinvention is limited solely by the appended claims.

What is claimed is:

1. A spray nozzle comprising body means formed with an inlet passage forreceiving the fluid to be sprayed and a bore, means forming a swirlchamber having a portion which is in the shape of an are, said swirlchamber having an inlet opening for communication with said bore, andorifice means having an outlet in communication with said swirl chamber,said nozzle having an actual flow rate (W and a spray cone angle (2 indegrees which are related to the ratio (x) of the nozzle inlet area(B.H.) to nozzle outlet area 1rD /4 by the relationships:

( Kref f1( P M 't ref f3 =f where:

B is the width of the tangential inlet close to the inlet opening of theswirl chamber,

D is the diameter of orifice means outlet,

H is the height of the swirl chamber,

AP is the actual pressure drop of the nozzle,

K is the nozzle discharge coefficient at a reference pressure drop,

C is a correction factor to relate the nozzle discharge coefiicient atthe reference pressure drop (K to the discharge coefficient at aparticular pressure drop,

2%,, is the spray cone angle at the reference pressure drop, and

is a correction factor relating the nozzle spray cone angle at thereference pressure drop to any pressure drop.

2. The method of constructing a spray type nozzle of the type having aswirl chamber at least a portion of which is in the shape of an arc of aspiral with a predictable patt rnation index value, comprising the stepsof forming a body with an inlet passage for receiving the fluid to besprayed, forming a swirl chamber having an inlet opening communicatingwith the inlet passage and forming an orifice means with an outlet incommunication with the swirl chamber to have the ratios of the followingparameters within the stated ranges where k through k are positive realnumber constants with k; being less than k k k and k k being less than kk and k k being less than k and it and k being less than k and D is thediameter of orifice means outlet, L is the thickness of the orificemeans at its outlet, R is the largest radius of the swirl chamber, and Sis the thickness of the rib formed by the inner wall of the swirlchamber at the swirl chamber inlet.

3. The method of claim 2 comprising the further step of constructing thenozzle with an inlet between said inlet passage and an inlet portion ofthe swirl chamber which inlet is generally tangential to an arcuateportion of the swirl chamber, the following ratios of parametersconstructed within the stated ranges to make the patternation index lessthan a certain value, where k through k are positive real numberconstants where k is less than k k, and k k is less than k and k and kis less than k, and where B is the width of the tangential inlet portionclose to inlet opening of the swirl chamber, and H is the height of theswirl chamber. 4. The method of claim 3 further comprising the step ofconstructing the nozzle with the following ratios of parameters withinthe stated ranges:

H Z k13 and I014 where k through k are positive real number constantsand wherein km is less than km, kn, km and k [(14 is less than [(10, kand k13 k is less than k and k and k is less than k 5. The method ofconstructing a logarithmic spray type nozzle with a predictablepatternation index value, said nozzle having an inlet passage forreceiving the fluid to be sprayed, a swirl chamber having an inletopening communicating with the inlet passage and an orifice means withan outlet in communication with the swirl chamber comprising the stepsof determining the nozzle parameters of inlet passage area (3-H) andorifice outlet area (1rD /4) for a given nozzle flow rate and coneangle, and constructing the nozzle with the ratios of the parameters B/D and H /D maintained within predetermined limits where :1 and a arepositive real number constants with a being less than a and B is thewidth of the tangential inlet close to the inlet opening of the swirlchamber,

D is the diameter of orifice means outlet, and

H is the height of the swirl chamber.

6. The method according to claim 5, further comprising the step ofconstructing the nozzle where the ratios of the parameters R/D and L/Dare also maintained within predetermined limits where a and 11 arepositive real number constants with a being less than a a and a 0 beingless than a and a and :1 being less than (1 and L is the thickness ofthe orifice means at its outlet,

and R is the largest radius of the swirl chamber.

7. The method according to claim 6, further comprising the step ofconstructing the nozzle with the ratios of the following parameterswithin the stated ranges:

where a through a are positive real number constants where w, is lessthan all of the other constants a is less than a through a and a a isless than al through a a is less than a through a a is less than a a aand a a is less than a a and a a is less than a and a and a is less thana within the limits R L S 1 5 a 5 a and 4 5 5 wherein D is the diameterof orifice means outlet,

L is the thickness of the orifice means at its outlet,

R is the largest radius of the swirl chamber, and

S is the thickness of the rib formed by the inner wall of the swirlchamber at the swirl chamber inlet,

and wherein k through k are each positive real number constants with kbeing less than k and k and k; and k each being less than k k and kwhereby a nozzle is formed in which the patternation index can bepredicted.

9. A spray nozzle according to claim 8 wherein the ratio of parametersof the swirl chamber means and the orific means of the nozzle have thefollowing range of values referenced back to water having an inlet gagepressure of 100 p.s.i. which permits the prediction of the nozzle interms of a patternation index value.

10. A spray nozzle comprising body means formed with an inlet passagefor receiving the fluid to be sprayed and a bore, means forming a swirlchamber having a portion which is in the shape of an arc of a curve,said swirl chamber having an inlet opening for communication with saidbore, and orifice means having an outlet in communication with saidswirl chamber, said swirl chamber means and said orifice means havingthe following ratios of the parameters and within the limits where D isthe diameter of orifice means outlet,

L is the thickness of the orifice means at its outlet,

R is the largest radius of the swirl chamber,

B is the width of the tangential portion of the inlet means close to theinlet opening of the swirl chamber H is the height of the swirl chamberand where h through h; are positive real number constants with k beingless than h h and h h being less than h and I1 and 11 being less than hwhereby a nozzle is formed in which the patternation index can bedescribed.

11. A spray nozzle as in claim 10 wherein the nozzle is constructed withthe ratios of the following nozzle parameters controlled so that theratios of the para-meters of the nozzle are held within the followinglimits:

and

H R f hg and hg where h through h; are predetermined positive realnumber constants, and

117 is less than h h h and I1 it is less than I2 h and h k is less thanit and h and 11 is less than I1 12. A spray nozzle according to claim 11wherein the nozzle has the following ratios of parameters:

R RH B H R referenced back to water having a gage pressure of psi. whichenables the description of the nozzle in terms of a patternation indexvalue.

13. A spray nozzle according to claim 10 wherein the nozzle has thefollowing ratios of parameters:

R L B H 12, 2.62, L82 and 4.77

referenced back to water having a gage pressure of 100 p.s.1.

14. A spray nozzle as in claim 13 wherein the selected ratios of theparameter values produce a patternation index for the nozzle of 30 orless.

15. A spray nozzle according to claim 1 wherein each of the constantshq, h and hg is less than any one of the constants h h and h.,; theconstant h is less than h and the constant k is less than h 16. A spraynozzle as in claim 15 wherein the selected parameter ratios produce apatternation index of 30 or less.

17. The method of constructing a spray nozzle comprising forming a bodywith an inlet passage for receiving the fluid to be sprayed and a bore,forming a swirl chamber having an inlet and a portion which is in theshape of an arc and with an inlet opening for comrnunication with thebore, and the swirl chamber, the inlet opening having a portion which isgenerally tangential to an arcuate portion of the swirl chamber at itsinlet opening, forming an orifice means having an outlet incommunication with the swirl chamber, and con- 19 structing the nozzlewith the parameters B, D, H, L, R and S of the nozzle where:

B is the width of the tangential inlet close to the inlet opening of theswirl chamber,

D is the diameter of orifice means outlet,

H is the height of the swirl chamber,

L is the thickness of the orifice means at its outlet,

R is the largest radius of the swirl chamber, and

S is the thickness of the rib formed by the inner wall of the swirlchamber at the swirl chamber inlet,

so that the parameters have the ratios L B H S b1 b2; 3; n 5; 6 1

wherein 12 through. b, are positive real numbers and wherein b is lessthan b through b and b and b, is less than b through b b is less than bthrough b b,; is less than b b and b 12 is less than 12 and b and b isless than b the patternation index delta of the nozzle being calculableby the formula:

where g through g are real number constants and K is also a constant.

18. The method of claim 17 further comprising the step of constructingthe nozzle so that the parameters have the following additional ratioswherein b through b are positive real numbers and b is greater than 11but less than b b is greater than b but less than b b is greater than bbut less than b 17,; is greater than 11 but less than b 19. The methodof determining parameters for a spray nozzle of the type having bodymeans formed with an inlet passage for receiving the fluid to be sprayedand a bore, swirl chamber means having a portion which is in the shapeof an arc and an inlet opening, said swirl chamber means also having aninlet means for communication between said bore and said inlet openingof said swirl chamber, said inlet means having a portion which isgenerally tangential to a portion of an arc of the swirl chamber at saidinlet opening and orifice means having an outlet in communication withsaid swirl chamber, said nozzle when operating also having an actualflow rate (W and a spray cone angle (2 1/) in degrees which are relatedto the ratio (x) of the swirl chamber inlet area (B.H) to nozzle area1rD /4 where:

20 B is the width of the tangential inlet close to the inlet opening ofthe swirl chamber, D is the diameter of orifice means outlet, H is theheight of the swirl chamber,

comprising the steps of operating a plurality of nozzles havingdifferent B and H parameters at different inlet fluid pressures whichproduce different actual pressure drops through the correspondingdifierent nozzles, measuring the actual flow rate (W of each of thenozzles operated at the diflerent pressures to determine the respectivenozzle discharge coefficient at the different pressures, measuring thespray cone angles (2,0) of the different nozzles at the differentpressures, and producing by machine from the measurements made thefunctions f f f and 71 of the following equations:

( ref=f1 =f2 ref=lf3 2 1 14 AP is the actual pressure drop of the nozzleK is the nozzle discharge coeflicient at a reference pressure drop C isa correction factor to relate the nozzle discharge coefficient at thereference pressure drop (K to the discharge coeflicient at a particularpressure drop,

M is the spray cone angle at the reference pressure drop, and

C is a correction factor relating the nozzle spray cone angle at thereference pressure drop to any pressure drop.

References Cited UNITED STATES PATENTS 2,218,110 10/1940 Hosmer et a].239-468 2,551,276 5/1951 'McMahan 239-403 3,182,916 5/1965 Schulz239-468 2,378,348 6/1945 Wilmes et a1 239-491 2,719,755 10/ 1955 Stanley239-492 X 2,751,253 6/1956 Purchas et al. 239-492 X 2,904,263 9/1959Tate et a1 239-494 3,013,731 12/1961 Carlisle 239-104 X 3,198,214 8/1965Lorenz 239-468 X FOREIGN PATENTS 760,972 11/1956 Great Britain.

LLOYD L. KING, Primary Examiner US. Cl. XJR. 239--468, 492, 494

